The present invention relates generally to corrugated paperboard and, more particularly, to a corrugated paperboard container having a fold region and method of making the same.
Corrugated paperboard has many uses, the most common of which is its use in making a multitude of different types of containers for shipping and storage. Such containers are made from single wall, double wall, and triple wall corrugated paperboard. The overwhelming majority of corrugated paperboard containers are constructed from single wall board. This category of container makes up approximately ninety percent of the entire market for corrugated paper containers. Containers constructed from double wall corrugated paperboard comprise approximately eight percent of the container market, while triple wall corrugated board comprises approximately two percent.
The basic form of corrugated paperboard is well known, having a structure consisting of corrugated paper medium interposed between single layer sheets of paper liner. Single wall board is comprised of a single layer of corrugated paper medium sandwiched between two single layer liners; double wall board has an additional corrugated paper medium and a third single layer liner; triple wall board includes a third corrugated paper medium and a fourth single layer liner. The corrugations of each medium are glued to the liners to provide structural rigidity.
Containers made from corrugated paperboard are relatively lightweight and offer good strength and stability. One benefit of corrugated paperboard is its ability to be fabricated quickly and inexpensively in comparison with containers made from other materials, such as wood or plastic. Corrugated paperboard containers also offer superb cushioning properties. It is known by those skilled in the art that, generally, corrugated board comprised of more layers or walls offer a greater ability to cushion the enclosed articles and provide greater structural rigidity. Therefore, heavy articles, such as bulk flowables or machinery, or fragile articles such as electronics, require containers made from double or triple wall board. Less fragile articles or articles having lighter weight in proportion to bulk require containers made from single-wall corrugated paperboard.
Various types and grades of paperboard are used to form the corrugated paper mediums and the liners. Paper used in the construction of the liner and corrugated medium varies in terms of paper composition, i.e., proportion of virgin pulp employed versus proportion of recycled pulp employed, and in terms of the weight of the paper (measured in pounds per thousand square feet). Choice of paper ultimately affects the strength of the corrugated paperboard, the weight of the board, and the thickness of the board. Thus, choice of material is critical in meeting the specific design criteria for a given application.
It has heretofore been recognized that when more strength, rigidity, or puncture resistance is needed, higher density liners or more layers of corrugation are required. Neither of these options, however, offers a complete solution. Higher density liners, while providing additional rigidity and puncture resistance, are generally only available to a weight of ninety pounds per thousand square feet. Additional layers of corrugation, on the other hand, while providing increased strength and rigidity, also add the drawback of increasing bulk or thickness. This is significant when one considers the cumulative effect of additional layers of corrugation when many containers are shipped within a larger shipping container.
Accordingly, there is a need in the corrugated board container industry to provide for greater strength and rigidity without significantly adding to the bulk of the container.
One essential characteristic of any corrugated paperboard is its ability to be bent or folded along predefined lines such that flat blanks, once cut to the desired shape, can be folded to define the bottom, side panels, and top of the container. Single-wall corrugated board is generally easily foldable in a direction either parallel or transverse to the direction of the corrugations of the medium. However, because the corrugations of the mediums in double and triple wall corrugated board are generally aligned in a direction parallel to one another, creating bends or folds in a direction transverse to the direction of the corrugations can prove difficult. This difficulty increases as the structural rigidity of the particular board increases.
Several solutions have been provided to enhance the foldability of corrugated board. It is well known to provide a crushed region or score line transverse to the direction of the corrugations such that the structural integrity of the corrugated medium, and thereby the board, is diminished to a point wherein the board is proportionally easier to bend along the score line. This solution is not entirely satisfactory for thick or heavy duty board, however, because the bending line is not clearly defined and may result in a bend that is unpredictable and uneven. Additionally, this method substantially weakens the container in the region of the bend. Moreover, the thick or heavy duty board will not stay in the bent position when merely a score line is used to form the bend region.
A similar solution has been provided wherein a fold region is scored, i.e., crushed in a narrow region in order to reduce resistance to bending. Although this method provides for a more predicable and defined fold, it nevertheless forces a large quantity of paper material into the interior of the fold region, thereby preventing the adjacent sides of the fold from achieving and maintaining a perpendicular relation to one another. This result is exacerbated where the blank is made from triple wall corrugated board as opposed to single or double wall board. This method also significantly reduces the strength of the container in the fold region.
A third solution has been to cut a V-shaped channel into double or triple wall board. The channel is cut into the board such that only a single wall corrugated layer composed of a medium sandwiched between two single layer liners remains at the bottom of the channel. This method solves the problem of forcing a large quantity of paper material into the interior of the fold region. However, this method introduces great difficulty in maintaining and removing the channel at exactly the appropriate depth so that sufficient material is removed to achieve the desired reduction in the force required to form a bend, but not damage the remaining materials.
Another solution has been to create a channel of square or rectangular cross section in triple wall corrugated board. Similar to the V-channel method, this method relies on removal of all but a single corrugated paper medium sandwiched between the liner that will be outermost in the completed bend and the next innermost liner. The channel is formed by wiping the adhesive from the liner in the region of the intended bend prior to forming the triple wall corrugated board. Two slits are then cut into the board through the liner that will be innermost in the completed bend and a scraper removes the material in the fold region down to the single remaining layer or wall. A scored region is then provided in the channel to facilitate bending of the final layer of board. This method provides the same advantages as the V-channel method, but, because some residual adhesive remains after wiping, also creates the same difficulties in removing the desired material without damaging the remaining material. Furthermore, the path along which the adhesive is wiped must be significantly wider than the cutout fold region, because, as the adhesive is wiped from the fold, a wave of adhesive is created which, during the assembly of the board, flows back into a portion of the wiped area. The result of creating a wiped region which is significantly wider than the cutout area is an area adjacent to the bend region that is structurally weaker than the surrounding board.
The present invention provides an improved bend region in a relatively high strength corrugated board wherein a cutout area having a generally square or rectangular cross section is formed but does not suffer from the inadequacies of the prior art. The bend region is formed by cutting all but the outermost single wall from the corrugated board. Prior to applying adhesive to the corrugations to secure the walls of the board together, a selected portion of the corrugations are compressed so that the compressed corrugations do not receive any adhesive. Then all but the outermost single wall is cut in the area of the compressed corrugations to allow the remaining walls to be readily removed by a vacuum process to create the bend region. Practice of the present invention results in a corrugated board of higher strength than the prior art and yet folds as easy as the prior art corrugated boards.